The instant invention is related to a Solar Heating System described in U.S. Pat. No. 4,428,362 issued Jan. 31, 1984. Both that patent application and this application pertain to passive solar heating units, and in particular tackle the problem of reverse flow at night when the heating chamber becomes cool.
Solar heaters are generally classified as either active or passive systems. Active systems use pumps and temperature control units to circulate hot water or other fluid heating medium from the solar collector to its hot water storage tank. Passive systems rely on the convection that naturally occurs when water which is heated in the collector rises to the top of the collector unit and then to the hot water tank which is generally stored above the collector in order to make the unit flow passively. With the hot water storage tank well above the collector, and when the collector becomes cool at night, the system stabilizes and there is no further circulation, as the cold water or other fluid stays in the lower reaches of the system (the collector), and the warmer fluid remains up in the insulated tank, which is generally on the roof.
Although this arrangement functions passively, it also requires the use of separate units and cannot be packaged into a single case for reduced material costs, ease in installation and improvements in operating efficiency without the aid of some type of check valve.
The development of an efficient, trouble-free check valve to prevent reverse flow from happening at night with the unitized tank and collector design has been the object of research for a number of years. The obvious solution to the reverse flow problem would be to provide some kind of gossamer membrane as a flap check valve in the system. However, because of the very weak convective forces, even the most gossamer of membranes used as a check flap unduly resist forward flow if it is sufficiently substantial to block reverse flow.
An effective and very clever check valve using only liquids has been devised and has been the subject of a number of patent claims. In essence, when the system is functioning in its forward, normal mode, somewhere in the tank-to-collector circulatory system is placed an upwardly directed pipe which terminates with its upper rim in a chamber right at the meniscus between the lower water body and an overlying, lightweight, imisible oil. Forward circulation is up through the pipe, which displaces the oil just enough to permit the flow of the water back downward to another passageway, away from the oil trap. However, when reverse flow is attempted, the lighter weight oil is drawn down into the pipe mentioned above, causing a negative pressure head which continually resists the reverse flow.
Although the stratefied imissible liquid check valve as described is effective and is definitely a positive check, it is also rather fragile and susceptible to malfunctions caused by rough or improper installation, and requires that exact angles be achieved so the pipe and its imissible liquid have the appropriate relationship.
The parent application for this continuation-in-part avoided the concept of the check valve entirely by providing a piping arrangement which, through the use of selectively exposing the water supply passageway to the collector to cold ambient temperatures and warm ambient temperatures, and to insulation from ambient temperatures, achieved a geometric configuration of piping which automatically established a net pressurehead which resisted reversed flow or circulation. That concept, the validity of which has been proven and which will be disclosed in a patent to be issued shortly, has been expanded in the instant application in different embodiments.